Alzheimer's disease is a progressive neurodegenerative disease characterized by the deposition of amyloid β protein (Aβ), accumulation of phosphorylated tau in a nerve cell (neurofibrillary tangle), and nerve cell death. In recent years, the number of patients with Alzheimer is increasing because of aging, but an effective treatment method has not been developed as yet. The therapeutic drugs for Alzheimer's disease which are currently used in the medical front are mainly acetylcholinesterase (AchE) inhibitors. While AchE inhibitors provide a certain, confirmed level of usefulness, since they aim to supplement depressed acetylcholine, the treatment with AchE inhibitor is merely a symptomatic therapy. Thus, the prompt development of a basic remedy and prophylactic drug has been strongly desired.
It has been clarified that the presence of allele ε4 of apolipoprotein E (ApoE) controlling the cholesterol metabolism is a strong risk factor of Alzheimer's disease [non-patent document 1: Science, vol. 261, 921-923, 1993]. After this finding, the correlation between plural gene polymorphisms bearing the expression of protein controlling the cholesterol metabolism and the onset frequency of Alzheimer's disease has been shown, suggesting the correlation between the cholesterol metabolism and Alzheimer's disease [non-patent document 2: Neurobiol. Aging, vol. 24, 421-426, 2003, non-patent document 3: Mol. Psychiatry, vol. 8, 635-638, 2003]. Moreover, it has been reported that Cyp46 (same as “cholesterol 24-hydroxylase (CH24H)”), which is cholesterol oxidase specifically expressed in the brain, is a risk factor of Alzheimer's disease [non-patent document 4: Neurosci. Lett., vol. 328, pages 9-12, 2002]. Furthermore, it has also been reported that Cyp46(CH24H) is expressed in periphery of deposited amyloid in Alzheimer patients [non-patent document 5: J. Biol. Chem., vol. 279, pages 34674-34681, 2004], 24S-hydroxycholesterol (24-HC), which is a metabolite thereof, increases in the brain spinal cord fluid (CSF) of Alzheimer patients [non-patent document 6: Neurosci. Lett., vol. 324, pages 83-85, 2002, non-patent document 7: Neurosci. Lett., vol. 397, pages 83-87, 2006] and that 24-HC induces cell death of SH-SY5Y cell, which is a human neuroblast line [non-patent document 8: Brain Res., vol. 818, pages 171-175, 1999], and rats treated with 24-HC into the cerebral ventricle showed impaired short-term memory, which is commonly observed in Alzheimer's disease, suggesting that hippocampal neurons were damaged by 24-HC [non-patent document 9: Neuroscience, vol. 164, pages 398-403, 2009]. These findings suggest that Cyp46(CH24H) is deeply involved in the pathology of Alzheimer's disease. Therefore, a compound that inhibits the activity of Cyp46 (CH24H) (i.e., Cyp46(CH24H) inhibitor) suppresses nerve cell death, Aβ increase, intracerebral inflammation and the like observed in Alzheimer's disease, by decreasing intracerebral 24-HC, and is promising as a therapeutic or prophylactic drug showing not only an improvement of symptom but also a suppression of progression. Moreover, it has been reported that AchE inhibitor clinically used as a therapeutic drug for Alzheimer's disease shows an improving effect on memory disorders induced by Aβ in mouse [non-patent document 10: British Journal of Pharmacology, vol. 149, pages 998-1012, 2006], and Cyp46(CH24H) inhibitor showing an improvement effect for memory disorders in Aβ overexpression animal model (APP transgenic mouse, APP/PS1 double transgenic mouse etc.) is promising as a therapeutic drug for Alzheimer's disease.
As a concept of the prestage of Alzheimer's disease, a mild cognitive impairment has been proposed, and about half of those having this disorder is said to progress into the Alzheimer's disease in the future. In recent years, it has been reported that 24-HC increases not only in patients with Alzheimer's disease but also in CSF of patients with mild cognitive impairment [non-patent document 7: Neurosci. Lett., vol. 397, pages 83-87, 2006]. This finding suggests that Cyp46(CH24H) is involved in the pathology of mild cognitive impairment, and therefore, a Cyp46(CH24H) inhibitor is promising as a new therapeutic drug for Alzheimer's disease or a prophylactic drug for the progression into the Alzheimer's disease.
In recent years, moreover, it has been reported that 24-HC in the blood increases before expression of the symptom in an autoimmune encephalomyelitis model, which is an animal model of multiple sclerosis which is one of the demyelination diseases in the central nervous system [non-patent document 11: J. Neurosci. Res., vol. 85, pages 1499-1505, 2007]. Multiple sclerosis is often developed in younger people of about 30 years old, and scarcely developed in the elderly of 60 years or older. It has also been reported that 24-HC increases in multiple sclerosis patients aging from 21 to 50 [non-patent document 12: Neurosci. Lett., vol. 331, pages 163-166, 2002]. These findings suggest that Cyp46(CH24H) is involved in the pathology of multiple sclerosis, and therefore, Cyp46(CH24H) inhibitor is promising as a new therapeutic or prophylactic drug for multiple sclerosis.
Traumatic brain injury (also referred to as TBI in the present specification) is a condition exerting an extremely harmful influence on the health of individual, for which no effective cure has been established. In the repair process following tissue damage in TBI, reconstruction of nerve cell membrane and distribution of intracerebral cholesterol activated along with the growth of glial cell are suggested [non-patent document 13: Proc. Natl. Acad. Sci. USA, vol. 102, pages 8333-8338, 2005]. In a rat TBI model, an enhanced expression of Cyp46(CH24H) after trauma has been reported [non-patent document 14: J. Neurotrauma, vol. 25, pages 1087-1098, 2008]. Moreover, it has also been reported that 24-HC injures nerve cells [non-patent document 8: Brain Res., vol. 818, pages 171-175, 1999], and therefore, Cyp46(CH24H) inhibitor is promising as a new therapeutic or prophylactic drug for TBI.
As a pathological significance of 24-HC in neurodegenerative diseases, an inflammatory gene expression-enhancing action in nerve cells has been reported [non-patent document 15: NeuroReport, vol. 16, pages 909-913, 2005]. In addition, it is suggested that an intracerebral inflammation reaction accompanied by activation of glial cell is a pathological change characteristic of neurodegenerative diseases [non-patent document 16: Glia, vol. 50, pages 427-434, 2005]. In recent years, a therapeutic effect by suppression of intracerebral inflammation has also been reported for neurodegenerative diseases such as Huntington's disease, Parkinson's disease and amyotrophic lateral sclerosis and the like [non-patent document 17: Mol. Neurodegeneration, vol. 4, pages 47-59, 2009]. Therefore, suppression of intracerebral inflammation by decreasing 24-HC by the inhibition of Cyp46(CH24H) is promising as a new therapeutic or prophylactic drug for neurodegenerative diseases such as Huntington's disease, Parkinson's disease, cerebral infarction, glaucoma, amyotrophic lateral sclerosis and the like.
Glaucoma is the main cause of blindness, and is considered a serious social problem. However, normal intraocular pressure type field stenosis, which is the major symptom of the disease, has no effective cure. In recent years, it has also been reported that gene polymorphism of Cyp46(CH24H) associated with high blood 24-HC is related to the risk of the onset of glaucoma [non-patent document 18: Invest. Ophthalmol. Vis. Sci., vol. 50, pages 5712-5717, 2009], and Cyp46(CH24H) inhibitor is promising as a therapeutic or prophylactic drug for glaucoma.
Spasm is a disease that occurs in fits along with abnormal electric excitement of intracerebral nerve cells. Spasm is also one of the characteristic clinical findings in Alzheimer's disease [non-patent document 19: Epilepsia, vol. 47, pages 867-872, 2006], and it has been reported that spasm is highly frequently developed in APP/PS1 double transgenic mouse which is one kind of Alzheimer's disease models due to Aβ overexpression [non-patent document 20: J. Neurosci., vol. 29, pages 3453-3462, 2012]. It has been reported that carbamazepine, which is a therapeutic drug for spasm, shows a short term memory improving effect in a Y-maze test using mouse spasm model [non-patent document 21: J. Neurol. Neurosurg. Psychiatry, vol. 48, pages 459-468, 1985]. Thus, in animal model with spasm symptoms, Cyp46(CH24H) inhibitor showing a short term memory improving effect is promising as a therapeutic or prophylactic drug for spasm.
Since schizophrenia shows a variety of psychological symptoms such as hallucination, delusion, excitation, manic-depressive state and the like, therapeutic drugs therefor have been developed from various angles. In recent years, it has been pointed out that changes in the cholesterol metabolism are involved in the abnormality of neural activity seen in schizophrenia [non-patent document 22: J. Psychiatry Neurosci., vol. 36, pages 47-55, 2011]. Since cytotoxic factors such as oxidative stress also contribute to the pathology of schizophrenia, nerve cell toxicity due to 24-HC may aggravate the symptoms [non-patent document 23: Psychoneuroendocrinology, vol. 28, pages 83-96, 2003]. Therefore, Cyp46(CH24H) inhibitor that inhibits metabolism of cholesterol into 24-HC in the brain is promising as a new therapeutic or prophylactic drug for schizophrenia.
Examples of the compound having a structure similar to the present compound include the following compounds.
Patent document 1 discloses the following compound:
wherein    X1, X2 and X3 are independently N, O, S, C or the like;    G1 is CRaRb, NR7, or optionally substituted nitrogen-containing heterocycloalkyl;    G2 is a single bond, optionally substituted alkyl or the like;    R1 is aryl, nitrogen-containing heteroaryl or the like;    R2 is optionally substituted alkyl, optionally substituted aryl, optionally substituted heteroaryl or the like;    R3 and R4 are independently H, halogen, optionally substituted alkyl or the like;    R5, R6, R7 and R8 are independently H, halogen, optionally substituted alkyl or the like;    R5 and R6 in combination optionally form oxo; and    Ra and Rb are independently H, halogen, optionally substituted alkyl or the like,as an agent for the treatment of inflammation disease, Alzheimer's disease and the like.
Patent document 2 discloses the following compound:
wherein    V is carbonyl or the like;    A is N or C(H);    R1 is H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl or the like;    R2, R2a, R3, R3a, R4, R4a, R5 and R5a are independently H, halogen, optionally substituted alkyl or the like;    R6 is —R8—OR10, optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted aryl, optionally substituted heterocycloalkyl, optionally substituted heteroaryl or the like;    R8 is a single bond, alkynylene or alkenylene; and    R9 and R10 are independently H, halogen, optionally substituted alkyl or the like,as an agent for the treatment of autoimmune diseases, Alzheimer's disease, age-related dementia and the like.
Patent document 3 discloses the following compound:
wherein    A-B is N—O, O—N or N(H)—N;    R1 is H, C1-8 alkyl, C1-8 alkoxy, hydroxy, halogen or the like;    R2 is H, aryl, heteroaryl, C1-6 alkyl or the like;    Q is a nitrogen-containing ring (the following formula (IIb) etc.)
    R6 is H, hydroxy, aryl or the like;    X, Y and Z are independently O, NR7 or CR72;    R7 is, H, C1-8 alkyl, C2-8 alkenyl, C1-4 alkoxy, heteroaryl-C1-6 alkyl, aryl-C1-6 alkyl or the like; and    n is 0-3,as an agent for the treatment of diseases associated with immune disease, dementia, hypertension, diabetes and the like (e.g., Alzheimer's disease etc.)
Patent document 4 discloses the following compound:
wherein    Ht is a heterocyclic group (pyrrol-3-yl, [1,2,4]triazol-3-yl, [1,2,3]triazol-4-yl or tetrazol-5-yl, the pyrrol-3-yl has R3 and Qn-R4, and the [1,2,4]triazol-3-yl or [1,2,3]triazol-4-yl has R3 or Qn-R4);    T and Q are independently —C(O)— or the like;    m and n are independently 0-1;    R2 is R or the like;    R3 is R7, halogen, cyano or the like;    R is a C1-6 hydrocarbon group, C6-10 aryl, C6-10 heteroaryl, C3-10 heterocycloalkyl or the like; and    R7 is H, an optionally substituted C1-6 hydrocarbon group or the like,as an agent for the treatment of autoimmune diseases, Alzheimer's disease and the like.